Vapor deposition apparatus

ABSTRACT

A vapor deposition apparatus for forming thin films on substrates with reactive gases, by rotating and revolving the substrates while heating the substrates in a reactor vessel, comprises a hollow susceptor carrier rotatably disposed inside the reactor vessel, susceptors rotatably disposed on the susceptor carrier to hold the substrates respectively, a driving motor for rotating the susceptor carrier such that the substrates held by the susceptors are revolved with respect to the reactor vessel, and a converting mechanism for converting a rotation motion of the susceptor carrier rotated by the driving motor into a motion for rotating the susceptors together with the substrates around themselves. The converting mechanism is disposed within the hollow of the susceptor carrier.

This application is a division of application Ser. No. 07/181,091, filedApr. 13, 1988 now U.S. Pat. No. 5,002,011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vapor deposition apparatus adoptedfor manufacturing compound semiconductor thin films on substrates, andparticularly to a vapor deposition apparatus which smoothly rotates andrevolves substrates to form thin films having uniform thicknessdistribution on the substrates.

2. Description of the Prior Art

There are several conventional vapor deposition apparatuses which aregenerally used to manufacture heterostructure compound semiconductors.Among such conventional apparatuses, FIGS. 1, 3 and 4 show vertical-typevapor deposition apparatuses, and FIG. 2 shows a horizontal-type vapordeposition apparatus.

In FIG. 1, a revolving turntable 5 is disposed in a silica reactor tube1 and rotated by a motor 6. On the turntable 5, there are disposed aplurality of susceptors 4 made of graphite material, etc. A rack 4aformed on the periphery of each of the susceptors 4 engages with a gear9. The gear 9 is rotated by a motor 7 to rotate the susceptors 4 and aplurality of substrates 3 respectively held by the susceptors 4. Thesusceptors 4 are heated by a high-frequency coil 2 disposed around thesilica reactor tube 1 to heat the substrates.

While the susceptors 4 are being rotated and revolved with thetemperature of the substrates 3 being maintained at a predeterminedvalue, reactive gases, for instance organometallic gases such as (CH₃)₃Ga, (CH₃)₃ Al and AsH₃, are alternately or simultaneously supplied froma gas supplying port 10 to grow crystals on the substrates 3 which aremaintained at the high temperature.

In such a vertical-type vapor deposition apparatus of the prior art, thesusceptors 4 are generally heated to about 700° C. to 800° C. to growthe crystals. As a result, if the quantity of each reactive gas issmall, heat convections are caused on the substrates 3 which generatevortexes that disturb the flows of the gases. If the flows are disturbeddue to these vortexes, the surfaces for growing crystals will notprovide heterostructures, leading to a deterioration in the electricalcharacteristics of the thin films to be formed on the substrates 3.Particularly, in growing ultrathin films, each having a crystal filmthickness of several 10Å, the reactive gases would be quickly changedfrom one to another, thereby causing serious problems due to heatconvections.

In the horizontal-type vapor deposition apparatus shown in FIG. 2, arevolving turntable 15 is disposed at the bottom of a reactor tube 11and rotated by a motor 16. On the turntable 15 there are disposed aplurality of susceptors 14 each holding and rotating a substrate 13. Arack 14a is formed on the periphery of each of the susceptors 14 andengages with a gear 19. The gear 19 is rotated by a motor 17 to rotatethe susceptors 14. The susceptors 14 are heated to a predeterminedtemperature by an infrared lamp 12 disposed outside the reactor tube 11,thereby increasing the temperature of the substrates 13 to apredetermined value. After that, reactive gases are supplied from a gassupplying port 20 in the same manner as described in the above to reactand grow crystals on the substrates 13.

In this horizontal-type vapor deposition apparatus, the reactive gasesflow horizontally to make a laminar flow such that the formation ofvortexes are not so significant and the disturbance in the flow isrelatively small. However, with respect to the gas supplying port 20,there is a large difference in the distance between a proximal portionand a distal portion of each of the substrates 13. Therefore, thecrystal growing rates of the proximal and distal portions of thesubstrate 13 differ from each other, resulting in unevenness in thethickness distribution of the film formed on the substrate 13.Particularly, in forming an ultrathin film on the substrate, thisproblem is not solved even if the substrate is rotated and revolvedbecause there are limits to the rotating and revolving speeds of thesubstrate and because reactive gases, each in small quantities, arechanged from one to another in short time intervals before the substrate13 can complete a single revolution. Namely, the reactive gases arechanged from one to another at a more rapid rate than that of the rateof revolution for the substrate 13. As a result, differences in thecomposition ratio and thickness distribution of a film to be formed onthe substrate are increased.

Since the area of the turntable 15 is large, the flows of the reactivegases are more disturbed as the revolving speed of the turntableincreases. In mass production, the number of substrates 13 is large, sothe area of the turntable 15 needs to be increased, thus increasing thesize of the vapor deposition apparatus.

FIGS. 3 and 4 are a general perspective view and a cross-sectional view,respectively, showing another vertical-type vapor deposition apparatus.

In the figures, a shaft 22 for supplying reactive gases is disposedsubstantially at the center of a reactor tube 21. A susceptor 23 issupported by a plurality of bases 24 arranged around the shaft 22. Thebases 24 are fitted to a hub 25 which is rotated by a motor (not shown)to rotate the susceptor 23. On an outer surface of the susceptor 23,there are rotatably disposed susceptor rotors 26 on each of which asubstrate 27 is mounted. The periphery of each susceptor rotor 26frictionally makes contact with a fixed track 28. When the susceptor 23is rotated, the susceptor rotors 26 are also rotated with respect to thefixed track 28. As a result, the substrates 27 are simultaneouslyrotated and revolved.

One feature of the vapor deposition apparatuses shown in FIGS. 1 through4 is the simultaneous rotation and revolution of substrates. However, acommon problem was found to exist in the above-mentioned prior arts,according to experiments carried out by the inventors, in that productsof reaction adhere to the substrate rotating mechanisms (e.g., the gears9 and 19, the racks 4a and 14aand the motors 6 and 16 of the apparatusesshown in FIGS. 1 and 2, and the peripheries of the susceptor rotors 26and the contacting portion of the fixed track 28 of the apparatus shownin FIGS. 3 and 4) exposed to the reactive gases in the reactor tubes,thereby hindering the smooth rotation and revolution of the substratesas time elapses, and thus causing unevenness in the thickness of thefilm formed on each substrate.

In the apparatus shown in FIGS. 3 and 4, when the susceptor 23 isinductively heated with a high-frequency coil, an induction currentflows through the susceptor 23 which is a conductor, and electricaldischarge phenomena are caused between the susceptor 23 and thesusceptor rotors 26 due to sliding motions between them. As a result,the contacting faces of the susceptor 23 and the susceptor rotors 26 arequickly worn, leading to a deterioration in the durability of theapparatus and thus increasing the need for frequent maintenance. Inaddition, due to the electrical discharges, high-frequency outputs varyand this destabilizes the temperature of the susceptor 23, whichsubsequently deteriorates the uniformity of the crystalline thin filmformed on each substrate 27.

SUMMARY OF THE INVENTION

An object to the present invention is to provide a vapor depositionapparatus which can form a thin film having a uniform thicknessdistribution.

Another object of the present invention is to provide a vapor depositionapparatus which can smoothly rotate and revolve substrates on which thinfilms are formed.

Still another object of the present invention is to provide a vapordeposition apparatus which can prevent products of reaction fromadhering to the mechanisms for rotating and revolving substrates onwhich thin films are formed.

Still another object of the present invention is to provide a vapordeposition apparatus which can improve the rotating characteristics ofsusceptors.

Still another object of the present invention is to provide a vapordeposition apparatus which can improve the durability of the mechanismsfor rotating and revolving substrates.

Still another object of the present invention is to provide a vapordeposition apparatus which can prevent electrical discharging phenomenafrom happening due to susceptors sliding on a susceptor carrier.

In order to accomplish the objects and advantages mentioned in theabove, the present invention provides a vapor deposition apparatus whichcomprises a reactor vessel, a hollow susceptor carrier rotatablysupported substantially at the center of the reactor vessel, a gassupplying port for supplying reactive gases to the reactor vessel, adischarging port for discharging the reactive gases out of the reactorvessel, susceptors rotatably supported by the susceptor carrier andholding substrates thereon respectively, a heater for heating thesusceptors to a predetermined temperature, a revolving mechanism forrevolving the susceptor carrier so that the substrates are revolved withrespect to the reactor vessel, a rotating mechanism for rotating thesusceptors to rotate the substrates around themselves, and drivingdevices for driving the revolving and rotating mechanisms. At least oneof the revolving and rotating mechanisms is disposed within the hollowof the susceptor carrier.

With the above-mentioned arrangement, the mechanisms for revolving androtating the susceptors are arranged within the hollow of the susceptorcarrier such that the mechanisms do not make contact directly with theflowing reactive gases. As a result, the products of reaction will notadhere to the mechanisms and, therefore, the susceptors can be stablyand smoothly rotated and revolved for long durations.

According to another aspect of the present invention, there is provideda vapor deposition apparatus for introducing reactive gases to a reactorvessel through a gas supplying port to grow new crystals on crystallinesubstrates disposed in the reactor vessel. The apparatus comprises asusceptor carrier rotatably supported in the reactor vessel, susceptorsrotatably supported by the susceptor carrier and on which thecrystalline substrates are mounted respectively, a rotating mechanismdisposed within the susceptor carrier to rotate the susceptors withrespect to the susceptor carrier, and a gas blowing device for blowing agas which does not influence a crystal growing reaction from thesusceptor carrier to the reactor vessel through gaps between thesusceptor carrier and the susceptors.

According to this aspect of the present invention, the gas which doesnot influence the crystal growing reaction is always blown through thegaps between the susceptors and the susceptor carrier so that productsof the reaction do not adhere around the gaps, thus maintaining aconsistently smooth rotation of the substrates.

According to still another aspect of the present invention, there isprovided a vapor deposition apparatus which comprises a reactor providedwith an introducing port and a discharging port of reactive gases, astationary shaft fixed in the reactor, a susceptor carrier rotatablewith respect to the stationary shaft, a heater for heating the susceptorcarrier, susceptors rotatable with respect to the susceptor carrier andholding crystalline substrates thereon respectively, a driving devicefor rotating the susceptor carrier such that the crystalline substratesheld by the susceptors are revolved with respect to the reactor, and aconverting mechanism for converting a motion of the susceptor carrierrotated by the driving device into a motion by which the susceptors andcrystalline substrates are rotated around themselves. By operating theheater and supplying reactive gases through the introducing port,crystalline thin films are formed on the crystalline substrates whichare revolved and rotated by the driving device. Between the susceptorcarrier and the susceptors, there are arranged electric insulatingmembers that make contact with the susceptor carrier and the susceptorsthrough their faces.

According to this aspect of the present invention, the susceptor carrieris rotated by the driving device to revolve the crystalline substrateswith respect to the reactor. The rotation of the susceptor carrier isconverted by the converting mechanism into a motion which rotates thecrystalline substrates around themselves. The susceptor carrier isheated by the heater to heat the crystalline substrates, and thereactive gases are introduced to the reactor through the introducingport to form crystalline thin films on the crystalline substrates.

Between the susceptor carrier and the susceptors, there are arranged theelectric insulating members whose surfaces make contact with thesusceptor carrier and the susceptors. Therefore, the susceptors do notslide directly on the susceptor carrier. As a result, electricaldischarges can be prevented from occurring due to incomplete contact ofthe susceptors with respect to the susceptor carrier.

These and other objects, features and advantages of the presentinvention will become apparent from the following descriptions ofpreferred embodiments taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a vertical-typevapor deposition apparatus according to a prior art;

FIG. 2 is a cross-sectional view schematically showing a horizontal-typevapor deposition apparatus according to a prior art;

FIGS. 3 and 4 are a perspective view and a cross-sectional partial view,respectively, showing another vertical-type vapor deposition apparatusaccording to a prior art;

FIG. 5 is a cross-sectional view schematically showing a vapordeposition apparatus according to a first embodiment of the presentinvention;

FIG. 6 is a cross-sectional view schematically showing a firstmodification of the first embodiment shown in FIG. 5;

FIG. 7 is a perspective view, partly sectioned, showing a vapordeposition apparatus according to a second embodiment of the presentinvention;

FIG. 8 is a perspective view, partly sectioned, showing a modificationof the second embodiment as shown in FIG. 7;

FIG. 9 is a cross-sectional view schematically showing a vapordeposition apparatus according to a third embodiment of the presentinvention;

FIG. 10 is an enlarged view showing part of the third embodiment asshown in FIG. 9;

FIG. 11 is an explanatory view showing a rotating and revolving state ofsusceptors of the third embodiment;

FIGS. 12 through 15 are cross-sectional views schematically showingsecond through fifth modifications, respectively, of the firstembodiment as shown in FIG. 5;

FIG. 16 is an explanatory view showing a rotating and revolving state ofsusceptors of the first embodiment;

FIG. 17 is a distribution diagram showing a comparison of filmthicknesses of thin films prepared by the vapor deposition apparatusesof the present invention and of the prior art; and

FIG. 18 is an overhead view schematically showing the susceptors of thefirst embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 5 shows a vapor deposition apparatus according to the firstembodiment of the present invention. The apparatus comprises a reactortube 31 within which a hollow revolving susceptor carrier 35 issupported by a rotary shaft 46. To maintain the reactor tube 31 disposedon a base 30 airtight, a seal acting as a bearing is used to rotatablysupport the rotary shaft 46 with respect to the base 30. The rotaryshaft 46 is connected to a motor 36 for rotating and revolving thesusceptor carrier 35 through the rotary shaft 46.

The susceptor carrier 35 has, for instance, a polyhedral, pyramidalshape to hold a plurality of substrates. On a peripheral slope of thesusceptor carrier 35 there are disposed a plurality of susceptors 34 andsubstrates 33 such that the susceptors 34 and substrates 33 aresubstantially in parallel with the flows of reactive gases which flowalong the reactor tube 31, i.e., substantially in parallel with an innerwall of the reactor tube 31. The susceptors 34 and substrates 33 arearranged inwardly on the periphery of the susceptor carrier 35. Each ofthe susceptors 34 is supported by one end of a supporting shaft 41 theother end of which is provided with a bevel gear 42. Each supportingshaft 41 is supported by the susceptor carrier 35 through a bearing suchas a slide bearing which will realize the stablest rotation of thesupporting shaft 41 under the high temperature conditions (about 800°C.) of a crystal growing process.

The rotary shaft 46 is surrounded by a hollow supporting shaft 38a towhich a receiver gear 43 is fixed to engage with the bevel gears 42 ofthe supporting shafts 41.

By driving the motor 36, the susceptor carrier 35 is rotated to revolvethe substrates 33 while the substrates 33 are being rotated aroundthemselves by the actions of the bevel gears 42 and receiver gear 43.

In this arrangement, rotating mechanisms such as the rotary shaft 46,bevel gears 42 and receiver gear 43 are received within a hollow of thesusceptor carrier 35 and isolated from a flowing region of the reactivegases to prevent products of reaction from adhering to the rotatingmechanisms. As a result, the substrates 33 are always smoothly rotatedand revolved.

The susceptors 34 are heated with a high-frequency coil 32 disposedoutside the reactor tube 31 to heat the substrates 33 to a predeterminedtemperature. After that, the reactive gases are supplied from a gassupplying port 40 to grow crystals on the substrates 33. The reactivegases are then discharged through a discharging port 48.

Since the front surface of each of the substrates 33 is substantially inparallel with the inner wall of the reactor tube 31, the reactive gasesflow in front of and substantially in parallel with the front surfacesof the substrates 33. Therefore, the substrates 33 will not beinfluenced by heat convections and vortexes are not caused, thusachieving favorable flows for the reactive gases.

The substrates 33 are arranged in a circumferential direction on theperipheral slope of the susceptor carrier 35 so that the respectivesubstrates 33 are equally distanced from the gas supplying port 40.Therefore, the thickness distributions and component ratios of filmsformed on the respective substrates 33 will be uniform throughout thefilms.

Since the front surfaces of the substrates 33 are disposed substantiallyin parallel with the inner wall of the reactor tube 31, an internalvolume of the reactor tube 31 can be reduced by narrowing the gapsbetween the substrates 33 and the reactor tube 31 to remarkably reducethe quantities of the reactive gases.

FIG. 6 is a view showing the first modification of the first embodimentas shown in FIG. 5. As shown in FIG. 6, the lower part of a susceptorcarrier 35 is open such that the apparatus is easily assembled. Thisopening of the susceptor carrier 35 is located on the downstream side ofthe flows of reactive gases in a reactor tube 31.

Even with the susceptor carrier 35 provided with the opening, productsof reaction will not adhere to rotating and revolving mechanisms becausethe opening is located on the downstream side of the flows of reactivegases. Therefore, the same effect as that of the first embodiment can beobtained with this modification. Due to the provision of the opening,the rotating and revolving mechanisms are easily arranged within ahollow of the susceptor carrier 35 to realize easy assembling andmaintenance.

FIG. 7 shows a vapor deposition apparatus according to the secondembodiment of the present invention.

In addition to the components of the apparatus of the first embodiment,the second embodiment apparatus is provided with a purge gas blowingmechanism for blowing a purge gas against rotating and revolvingmechanisms to prevent products of reaction from adhering to themechanisms. In FIG. 7, the parts that are same as those of the firstembodiment are represented with like reference numerals to omit theirexplanations.

The purge gas blowing mechanism comprises a purge gas introducing groove52 passing through a seal bearing 50 for sealing a reactor tube 31. Inthe seal bearing 50 and above and below the groove 52, there arearranged seals 54 and a bearing portion 56. A purge gas introducing pipe58 is connected to the groove 52. A gas passage 60 is formed in a rotaryshaft 46 to extend from the vicinity of the groove 52 to the top of therotary shaft 46. An opening 60a of the gas passage 60 communicates withthe groove 52. At the top of the rotary shaft 46, distribution passages62 are formed to communicate with a susceptor carrier 35 and respectivesusceptors 34. Crystalline substrates 33 respectively fitted to thesusceptors 34 are heated with a high-frequency coil 32.

With this arrangement, reactive gases such as arsine andtrimethylgallium (TMG) are supplied through a reactive gas supplyingport 40 and are heated together with the susceptors 34. When thereactive gases pass over the crystalline substrates 33 tightly fitted tothe peripheral surfaces of the susceptor 34, the gases are decomposedand form crystals of gallium arsenide on the surfaces of the substrates33.

To obtain uniform crystalline thin films on the crystalline substrates33 in order to provide satisfactory semiconductor elements, thesubstrates 33 are rotated and revolved. If the reactive gases flow intothe gaps between the susceptors 34 and the susceptor carrier 35,reaction products may become deposited on the susceptors 34 and thesusceptor carrier 35 around these gaps, because the susceptors 34 andthe susceptor carrier 35 are also heated. If so, the rotating andrevolving mechanisms will not be smoothly driven, leading todeterioration in the uniformity of the film thicknesses.

To cope with this problem, the second embodiment of the presentinvention supplies the purge gas to the groove 52 through the pipe 58.The purge gas is passed through the passage 60 in the rotary shaft 46and through the distribution passages 62 in the susceptor carrier 35,and is blown into the gaps between the susceptor carrier 35 and thesusceptors 34. The purge gas fills the gaps between the susceptorcarrier 35 and the susceptors 34, and is blown toward the surface of thesusceptor carrier 35 and discharged together with the reactive gasesthrough a gas discharging port 64.

As a result, the reactive gases do not flow into the gaps between theperipheries of the susceptors 34 and the susceptor carrier 35, and sothe crystalline substrates 33 are always smoothly rotated and revolved.Even if the concentrations of the reactive gases vary, remarkablyuniform crystalline films can be grown on the crystalline substrates 33to improve the yields.

In this embodiment, the purge gas is a gas which does not influence thegrowth of crystals and is a carrier gas or an inert gas (H₂, N₂ or Ar).The purge gas is supplied in small quantities so as not to disturb theflows of reactive gases.

FIG. 8 shows a modification of the second embodiment.

According to this modification, a communication passage 68 is formed atthe top of the gas passage 60 of the rotary shaft 46 of the secondembodiment. The communication passage 68 connects the passage 60 to aninner space 66 of the susceptor carrier 35.

By virtue of the communication passage 68, the purge gas is directlyguided to the inside of the susceptor carrier 35 to completely preventthe products of reaction from adhering to the rotating and revolvingmechanisms disposed inside the susceptor carrier 35.

Although both the distribution passages 62 and the communication passage68 have been provided for the embodiment shown in FIG. 8, thedistribution passages 62 may be omitted to provide only thecommunication passage 68. Even with the communication passage 68 only,the inside of the susceptor carrier 35 is filled with the purge gas toprevent the products of reaction from adhering to the rotatingmechanisms. If a large part of the purge gas is discharged through thelower part of the susceptor 35, the purge gas will not disturb the flowsof the reactive gases.

FIGS. 9 through 11 show a vapor deposition apparatus according to thethird embodiment of the present invention.

The third embodiment shown in FIG. 9 is provided with an electricinsulating member 70 between the susceptor carrier 35 and each of thesusceptors 34 of the first embodiment to prevent electrical dischargephenomena. In the figure, the same components as those of the firstembodiment are represented with like reference numerals to omit theirexplanations.

FIG. 10 shows the details of the third embodiment. The electricinsulating member 70, made of, for instance, boron nitride, is disposedbetween the susceptor carrier 35 and each of the susceptors 34. Eachinsulating member 70 comprises a cylindrical bearing portion 70a, afirst plate portion 70b and a second plate portion 70c.

The bearing portion 70a is interposed between an insertion hole 72 ofthe susceptor carrier 35 and a supporting shaft 41 of the susceptor 34.The first plate portion 70b is interposed between the susceptor carrier35 and a main portion 74 of the susceptor 34. The second plate portion70c is interposed between the susceptor carrier 35 and a bevel gear 42of the susceptor 34. The susceptor carrier 35 and the susceptor 34 makecontact with the surfaces of the insulating member 70, and are thereforeseparated from each other by the insulating member 70 lying betweenthem.

Around the periphery of a reactor tube 31, there is disposed ahigh-frequency coil 32. When the high-frequency coil 32 is energized, aninduction current flows through the susceptor carrier 35 to heat thesusceptor carrier, thus heating the substrates 33.

An operation of the third embodiment will be described.

The rotary shaft 46 is rotated by a motor 36 to rotate the susceptorcarrier 35 and to revolve the substrates 33 with respect to the reactortube 31. At this time, the bevel gears 42 of the susceptors 34 arerotated with respect to a receiver gear 43 to rotate the substrates 33around the supporting shafts 41 (FIG. 11). Since the insulating members70 act as bearings between the susceptor carrier 35 and the susceptors34, the susceptors 34 are smoothly rotated.

The susceptor carrier 35 is heated with the high-frequency coil 32 toheat the substrates 33. While the substrates 33 are being rotated andrevolved as mentioned in the above, the temperature of the substrates 33is increased to a predetermined value. Then, reactive gases such as(CH₃)₃ Ga are introduced from an introducing port 40 to grow thincrystalline films on the substrates 33.

When the susceptor carrier 35 is heated with the high-frequency coil 32,induction currents flow through conductive members, i.e., the susceptorcarrier 35, susceptors 34, the receiver gear 43 and bevel gears 42.However, by virtue of the electric insulating members 70 disposedbetween the susceptor carrier 35 and the susceptors 34, the conductivemembers do not directly slide on each other thereby preventingelectrical discharges. Since electric discharges are suppressed,high-frequency outputs will not vary, and so the temperature of thesusceptor carrier 35 is stabilized, the substrates 33 are smoothlyrotated and revolved, and the thin crystalline films uniformly formed onthe substrates 33.

The insulating members 70, made of, for instance, boron nitride, havelow coefficients of friction so that the susceptor carrier 35 and thesusceptors 34 are not worn easily, thus improving their durabilities andreducing their maintenance frequencies.

Engaging portions between the receiver gear 43 and the bevel gears 42are disposed in a hollow of the susceptor carrier 35 in such a way thatthe reactive gases hardly influence these portions, and so the productsof reaction hardly adhere to the engaging portions. Since the productsof reaction do not adhere to the engaging portions of the receiver gear43 and the bevel gears 42, the substrates 33 are smoothly rotated andrevolved to form uniform, thin crystalline films on the substrates 33.

Each of the substrates 33 is arranged substantially parallel to an innerwall of the reactor tube 31 so that the reactive gases flow in parallelwith the surfaces of the substrates 33. Therefore, the generation ofheat convections can be suppressed to prevent the generation of vortexesand turbulence, and thereby achieve satisfactory gas flows. Since thesubstrates 33 are disposed substantially parallel to the inner wall ofthe reactor tube 31, an internal volume of the reactor tube 31 can bereduced to conserve the reactive gases and reduce the overall size ofthe reactor tube 31.

The present invention is not limited to the above mentioned embodiments,instead various modifications may be possible without departing from thescope of the present invention. For instance, the electric insulatingmembers 70 can be constituted with two components, and many kinds ofelectric insulating material may substituted in place of boron nitride.Further, the bearing portion 70a of each insulating member 70 maycomprise a slide bearing or a ball bearing. The slide bearing is mostpreferable under high temperature conditions. Friction wheels maybesubstituted for the gears of the converting mechanisms for generatingrotational motions. The shape of the susceptor carrier 35 is not limitedto only the polyhedral pyramid, instead it may be a polyhedral pyramidfrustum, a cone, a conical frustum, or a cylinder, with the onlyrequirement being subjected that the shape can provide the same effectas the polyhedral pyramid.

The shape of the reactor tube 31 may be a cylinder. In this case, gapsbetween the substrates 33 and the reactor tube 31 will be graduallynarrowed toward the downstream side of the direction of gas flow, thuswidening the selection range of conditions, such as the pressure andflow rate of reactive gases, to obtain a uniform film thicknessdistribution.

FIGS. 12 through 18 show the modifications of the first embodiment.

FIG. 12 shows the second modification of the first embodiment. In areactor tube 31, there is disposed a hollow susceptor carrier 35. Thesusceptor carrier 35 is supported by a supporting shaft 38 and isrotatable due to a bearing 39. The susceptor carrier 35 has, forinstance, a polyhedral pyramid shape to hold a plurality of substrates33. The substrates 33 are fitted to susceptors 34 which are disposed ona peripheral slope of the susceptor carrier 35. The substrates 33 andsusceptors 34 are inwardly disposed on the peripheral slope of thesusceptor carrier 35 and substantially in parallel with the flows ofreactive gases flowing along the reactor tube 21, i.e., substantially inparallel with an inner wall of the reactor tube 31. Each of thesusceptors 34 is supported by one end of a supporting shaft 41. Theother end of the supporting shaft 41 is connected to a bevel gear 42which engages with a receiver gear 43 fixed to the supporting shaft 38.

A pinion gear 44 is fitted to a motor 36 and engaged with a rack 45formed at the lower part of the susceptor carrier 35. By driving themotor 36, the susceptor carrier 35 is rotated to revolve and rotate thesubstrates 33 due to the actions of the bevel gears 42 and receiver gear43.

In this arrangement, the motor 36, pinion gear 44 and rack 45 of themechanisms for rotating and revolving the substrates 33 are disposed atthe lower part of the susceptor carrier 35 apart from the substrates 33over which the reactive gases flow. Therefore, products of reaction donot adhere to the mechanisms.

The bevel gears 42 and receiver gear 43 for rotating and revolving thesubstrates 33 are arranged in a hollow of the susceptor carrier 35 sothat the products of reaction do not adhere to the gears 42 and 43. Thebevel gears 42 and receiver gear 43 can be easily assembled into thesusceptor carrier 35 constituted with halved portions.

FIG. 13 shows the third modification of the first embodiment. A bearing37 which also acts as a seal closes a gap between the susceptor carrier35 and each of the susceptor supporting shafts 41 of the apparatus shownin FIG. 12 such that the reactive gases do not enter into the inside ofthe susceptor carrier 35.

FIG. 14 is a view showing the fourth modification of the firstembodiment. The fourth modification differs from the second modificationin that the motor 36 for rotation and revolution is disposed outside thereactor tube 31. A supporting shaft 38 is stationary, and a rotary shaft35a provided integrally with a susceptor carrier 35 is rotated to rotateand revolve the substrates 33.

Since the motor 36 for rotation and revolution is disposed outside thereactor tube 31, the products of reaction are completely prevented fromadhering to the rotating mechanisms, and the motor 36, etc., can bemaintained from the outside of the reactor tube 31.

FIG. 15 is a view showing the fifth modification of the firstembodiment. In the fifth modification, reactive gases do not flow inparallel with the surfaces of substrates 33. Even so, a uniform filmthickness distribution can be realized by smoothly rotating andrevolving the substrates 33 as shown in FIG. 16.

FIG. 17 shows measurement results of the thickness distributions offilms prepared according to the present invention compared with theconventional deposition method. The measurements obtained by using theconventional method were based on the assumption that the rotation of asubstrate on which a film is to be formed is hindered due to theproducts of reaction adhering to the rotating mechanisms of thesubstrate. Namely, the measurement process by the conventional methodwas carried out only by revolving the substrate. In the figure, opensymbols represent the thickness distributions of a film preparedaccording to the present invention, and black symbols correspond tothose of a film prepared according to the conventional method.

FIG. 18 is a conceptual view schematically showing a vapor depositionapparatus in which a substrate is obliquely held on a susceptor. Thereactor tube of the apparatus has a circular shape along a horizontalcross section. Irrespective of the shape of the susceptor, thehorizontal distance from an end portion of the substrate to an innersurface of the reactor tube is "l" and the horizontal distance from amiddle portion of the substrate to the inner surface of the reactor tubeis "l + a". Therefore, the flow rate of reactive gas at the middleportion is larger than that at the end portion. Accordingly, if thesubstrate is not rotated, the film thickness at the middle portion ofthe substrate becomes larger than that at the end portion.

However, if the substrate is smoothly rotated as in the case of thepresent invention, horizontal end portions of the substrate willsuccessively come to the middle position so that differences in the filmthickness distribution are averaged to realize a uniform film thickness.

The distance from the reactive gas supplying port to the proximal end ofthe substrate differs from the distance from the gas supplying port tothe distal end of the substrate by one diameter of the substrate. Thismay lead to differences in the concentration of a reactive gas at theproximal and distal locations, thus affecting the thickness of the filmto be formed on the substrate. Such differences can also be averaged bysmoothly rotating and revolving the substrate to realize a uniform filmthickness distribution.

By smoothly rotating the substrates 33, unevenness in film thicknessdistribution that may be caused on the substrates 33 due tomanufacturing errors of the reactor tube 31, susceptor carrier 35, etc.,can be prevented. Thus, uniformity of the substrates 33 is also secured.This is advantageous particularly in the mass production of thin films.

Compared with conventional apparatuses which hold substrateshorizontally, a larger number of substrates can be held withoutincreasing a diameter of the reactor tube by arranging the substrates ina sloped fashion to minimize the size of the apparatus.

As shown in FIG. 15, gaps between the substrates 33 and the reactor tube31 may be narrowed toward the downstream side of the flows of reactivegases, taking into account changes in the concentration of the reactivegases due to the growth of crystals. With this arrangement, theselection range of pressure, flow rate, etc., to obtain a uniform filmthickness distribution is widened.

In the third through fifth modifications of the first embodiment, it ispossible to add the purge gas blowing mechanism of the second embodimentor the electric insulating member for preventing electrical dischargesof the third embodiment to the modifications.

The present invention is not limited by the embodiments andmodifications described in the above, instead various modifications andalterations will be possible without departing from the scope of thepresent invention.

For instance, the shape of the susceptor carrier is not limited to justthe polyhedral pyramid and the polyhedral pyramid frustum. On thecontrary, it can be a cone, a conical frustum, or a cylinder as that ofthe prior art shown in FIGS. 3 and 4, with the requirement that thesusceptor carrier be hollow enough to accommodate rotating and revolvingmechanisms within it such that products of reaction can be preventedfrom adhering to these mechanisms.

Although only the bevel gear and receiver gear of the rotating mechanismhave been disposed inside the susceptor carrier, the revolving mechanismcan also be disposed inside the susceptor carrier.

In summary, according to the present invention, mechanisms for rotatingand revolving substrates are smoothly rotated, without products ofreaction becoming adhered to the mechanisms, to uniformalize filmthickness distributions of the substrates.

According to the present invention, a purge gas is blown into the gapsformed at the rotating and sliding portions of a susceptor carrier andsusceptors so that products of reactive gases are not deposited aroundthe gaps, which keeps the gaps clean. As a result, the susceptors aresmoothly rotated. Therefore, the thickness of a crystalline film formedon a crystalline substrate will be remarkably uniform.

Further, according to the present invention, an electric insulatingmember is disposed between a susceptor carrier and each of susceptors.The surfaces of each insulating member make contact with the susceptorcarrier and the susceptor such that the abrasion of the susceptorcarrier and the susceptors is suppressed to improve their durabilities.Therefore, the frequency of servicing is reduced to realize easymaintenance. When the susceptors are heated with high-frequency heaters,electrical discharges between the susceptor carrier and the susceptorsare suppressed by the insulating members to reduce variations inhigh-frequency outputs. Therefore, the temperature of the susceptors isstabilized, and uniform, thin crystalline films are formed on thesubstrates.

Various modifications will become possible for those skilled in the artafter receiving the instructions of the present disclosure withoutdeparting from the scope thereof.

What is claimed is:
 1. A chemical vapor deposition apparatus for formingthin films on substrates with reactive gases by rotating and revolvingthe substrates while heating the substrates in a reactor vessel,comprising:(a) a hollow susceptor carrier rotatably disposed inside thereactor vessel, said hollow susceptor carrier having an opening on adownstream side in relation to the reactive gas flow; (b) susceptorsrotatably disposed on said susceptor carrier to hold the substratesrespectively; (c) means for rotating said susceptor carrier; and (d)means located within a hollow of said susceptor carrier for rotatingsaid susceptors with respect to said susceptor carrier.
 2. The chemicalvapor deposition apparatus as claimed in claim 1, wherein said susceptorcarrier rotating means comprises driving means for rotating saidsusceptor carrier such that said substrates held by said susceptors arerevolved with respect to the reactor vessel, and said susceptor rotatingmeans comprises a converting mechanism for converting a rotating motionof said susceptor carrier rotated by said driving means into a motionfor rotating said susceptors together with the substrates aroundthemselves.
 3. The chemical vapor deposition apparatus as claimed inclaim 2, wherein the converting mechanism of said susceptor rotatingmeans is received within said hollow of said susceptor carrier.
 4. Thechemical vapor deposition apparatus as claimed in claim 1, wherein saidsusceptor rotating means is disposed within the hollow of said susceptorcarrier.
 5. The chemical vapor deposition apparatus as claimed in claim1, wherein said susceptors are rotatable with respect to said susceptorcarrier through slide bearings.
 6. The chemical vapor depositionapparatus as claimed in claim 4, wherein said susceptor carrier isarranged such that the front surfaces of the substrates held by saidsusceptors are substantially in parallel with the direction of thereactive gas flow in the reactor vessel.
 7. The chemical vapordeposition apparatus as claimed in claim 4, wherein said susceptorcarrier is arranged such that the front surfaces of the substrates heldby said susceptors are substantially in parallel with an inner wall ofthe reactor vessel.
 8. The chemical vapor deposition apparatus asclaimed in claim 2, wherein said driving means of said susceptor carrierrotating means comprises a driving motor.
 9. The chemical vapordeposition apparatus as claimed in claim 1, further comprising electricinsulating members disposed between said susceptor carrier and saidsusceptors to contact with said susceptor carrier and said susceptors.10. The chemical vapor deposition apparatus as claimed in claim 9,further comprising a high-frequency heater for heating said susceptorcarrier.
 11. The chemical vapor deposition apparatus as claimed in claim10, wherein said insulating members are made of boron nitride.
 12. Achemical vapor deposition apparatus comprising:a reactor vessel forreceiving a reactive gas in order to form a stream of said reactive gastherein; a substrate holder located in said stream for supporting asubstrate to be coated in a side of said holder which is located alongand exposed to said stream; a mechanism provided in an opposite side ofsaid substrate holder located apart from said stream in order to revolvesaid substrate; and an energy source for activating said reactive gas inorder to carry out deposition on said substrate, wherein said oppositeside is opened to the downstream of said stream.
 13. The apparatus ofclaim 13 wherein said substrate holder is a hollow pyramid opened to thedownstream.
 14. The apparatus of claim 13 wherein said stream is formedbetween said hollow pyramid and said vessel.